Solar tracking apparatus and field arrangements thereof

ABSTRACT

A solar tracker assembly for mounting one or more solar tracking units, which can be adapted for use with various solar energy modules such as photovoltaic modules and heliostat mirrors, is provided. Each assembly comprises a frame of four sides connected at leg assemblies, each leg assembly being adapted for mounting a solar tracking unit. The frame may be configured as an oblique-angled, rhombus or diamond frame with a cross member extending between the closer-spaced leg assemblies. A set of frames may be arranged in the field with adjacent sides of adjacent frames being parallel, with spacing arms of predefined lengths interconnecting adjacent pairs of frames, to provide a desired hexagonal grid spacing.

REFERENCE TO PRIOR APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/732,044 filed 30 Nov. 2012, the entirety of which is incorporated byreference. This application further incorporates the entireties of U.S.Provisional Applications Nos. 61/523,817 filed 15 Aug. 2011 and to61/532,083 filed 7 Sep. 2011 and PC′I′ application PCT/IB2012/052723filed 30 May 2012 by reference.

TECHNICAL FIELD

The present disclosure relates to the field of solar energy, and inparticular to tracking solar tracking assemblies, and arrangementsthereof.

Solar power is typically captured for the purpose of electrical powerproduction by an interconnected assembly of photovoltaic (PV) cellsarranged over a large surface area of one or more solar panels. Multiplesolar panels may be arranged in arrays.

In addition to the difficulties inherent in developing efficient solarpanels capable of optimum performance—including inconsistencies inmanufacturing and inaccuracies in assembly—field conditions pose afurther obstacle to cost-effective implementation of solar energycollection. Conventionally, solar tracker systems, which include atracker controller to direct the positioning of the solar panels,benefit from mounting on a flat surface permitting accurate mounting ofthe system and ensuring stability by anchoring the system to a securefoundation, for example by pouring a concrete foundation. Theserequirements, however, add to the cost of field installation because ofthe additional equipment and manpower requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate by way of example only select embodimentsthat are described herein,

FIG. 1 is a perspective view of a ground-based tracking solar panelassembly;

FIG. 2 is a perspective, partially exploded view of a box frame portionof the assembly of FIG. 1 in a deployed state;

FIG. 3 is a perspective view of a portion of the box frame of FIG. 2 ina collapsed state;

FIG. 4 is a perspective view of a leg assembly for mounting to a trussof the box frame of FIG. 2;

FIGS. 5, 6 and 7 are perspective views of alternate frameconfigurations;

FIG. 8 is a perspective view of an armature assembly for use with theassembly of FIG. 1;

FIGS. 9 and 10 are side elevations of example solar panels for use withthe assembly of FIG. 1;

FIGS. 11 and 12 are perspective views of a mounted photovoltaic trackermodule from the assembly of FIG. 1;

FIG. 13 is an illustration of an example of a plurality ofinterconnected frames;

FIG. 14 is a schematic showing electrical and communicationinterconnections among a plurality of tracking solar panel assemblies ofFIG. 1;

FIG. 15 is a flowchart illustrating a process for auto-calibration;

FIG. 16 is a further schematic showing electrical and communicationinterconnections among a plurality of tracking solar panel assemblies ina solar farm;

FIG. 17 is a perspective view of a ground-based tracking solar panelassembly;

FIG. 18 is a perspective view of a ground-based tracking assemblyincluding a frame and armatures;

FIG. 19A is a perspective view of a leg assembly of the solar panelassembly of FIG. 17;

FIGS. 19B and 19C are detail views of the leg assembly of FIG. 19A;

FIG. 20 is a perspective view of the frame of FIG. 17 in a collapsedstate;

FIG. 21 is a perspective view of the frame of FIG. 17 partiallydisassembled;

FIG. 22A is a side view of the frame and armatures of FIG. 18;

FIG. 22B is another side view of the frame and armatures of FIG. 18;

FIG. 23 is a perspective of an example of a plurality of interconnectedframes;

FIG. 24A is a perspective view of an example of a ground-based trackingsolar panel assembly;

FIG. 24B is a side view of an example of a ground-based tracking solarpanel assembly;

FIG. 24C is a top view of an example of a plurality of interconnectedframes;

FIG. 25A is a top view of an example of a field of interconnected framesin a first arrangement and orientation;

FIG. 25B is a top view of the field of FIG. 25B in a second orientation;

FIGS. 25C to 25E are top views of the field of FIG. 25B overlaid bydiamond and hexagonal grids;

FIG. 26A is a top view of an example of a field of interconnected framesin a second arrangement;

FIGS. 26B and 26C are top views of the field of FIG. 26A overlaid byrectangular and hexagonal grids, respectively;

FIG. 27A is a top view of an example of a field of interconnected framesin a third arrangement;

FIGS. 27B and 27C are top views of the field of FIG. 27A overlaid by ahexagonal grid;

FIG. 28 is a perspective view of an armature assembly for use with theassembly of FIGS. 17 and 18;

FIG. 29A is a perspective view of a frame of a ground-based trackingassembly with a length-adjustable cross member;

FIG. 29B is a detail view of the cross member of the tracking assemblyof FIG. 29A; and

FIG. 29C is a detail view of a leg assembly of the tracking assembly ofFIG. 29A.

DETAILED DESCRIPTION

A self-ballasted solar tracker assembly is provided for concentrated ornon-concentrated photovoltaic solar panels to maintain stability andalignment of the panels without requiring ground preparation. A modular,collapsible truss structure is provided as a frame to support aplurality of solar tracking units on which solar panels may be mounted.These individual panels are mounted at or near their center of gravityand positioned at corners or junctions of the frame. These structuresare physically interconnectible in the field for enhanced stability,thus reducing or eliminating the need for external ballast (such asconcrete blocks), and also for the purpose of facilitating electricalconnection and data communication. Arrangement of a plurality of theseinterconnected structures in a solar farm or sub-farm provides forefficiency in grounding the supporting structures of the solar trackingunits.

Turning to FIG. 1, a perspective view of a solar tracker assembly orunit 100 is shown. The assembly 100 generally includes a ground-mountedframe 10 for supporting one or more solar tracking units 200, such asthe photovoltaic (PV) tracker modules illustrated in FIG. 1. In theexample illustrated in FIG. 1, the solar tracking units 200 are shownsupporting solar panels 205. The frame 10 includes a plurality oftrusses 12, 22. In the example of FIG. 1, the frame 10 has a first pairof trusses 12, 12 of substantially equal length defining first opposingsides of the frame 10, joined to a second pair of trusses 22, 22 also ofsubstantially equal length defining the remaining opposing sides via legassemblies 30. The assembly of the trusses thus yields an overallparallelogrammatic, and in this specific example, a box or rectangularframe 10. The sides of the frame 10 need not employ trussesspecifically, although the benefits of the structural stability of atruss design will be appreciated by those skilled in the art.

As shown in FIG. 2, each individual truss 12 includes an upper chordmember 14 and lower chord member 16, and each individual truss 22includes an upper chord member 24 and lower chord member 26. The chordmembers 14, 16 and 24, 26 are joined by a set of truss members 17, 27respectively. Trusses 12, 22 in this example each include a set of fourtruss members 17, 27. The selection and arrangement of the truss members17, 27 need not be limited to the example shown; depending on theselected dimensions and materials of the frame 10, more or fewer trussmembers 17, 27 may be employed. In addition, one or more struts 18, 28may be mounted between the upper and lower chord members 14, 16 or 24,26 to provide additional vertical support between the chord members. Inthe example of FIG. 2, some struts 18, 28 are provided near the ends ofthe trusses 12, 22, i.e., near the joints between adjacent trusses. Thenumber (which may be zero or more) and arrangement of struts, as well asthe number and arrangement of truss members, can be selected accordingto the specific requirements for the solar tracker assembly 100installation, as well as inherent characteristics of the frame 10 andthe tracker modules 200, including the weight of the tracker modules 200to be supported, material used to fabricate the trusses 12, 22 and thegeometry of the trusses 12, 22.

The trusses 12, 22 are joined at or near their respective ends at legassemblies 30, shown in further detail in FIGS. 3 and 4. Each legassembly 30 includes a shaft 31, and can include an adjustable footmember 37, as shown in one example of the leg assembly as illustrated inFIG. 2. The foot member 37 in this example is detachable and includes aplate member 39 extending from a stem 38. The stem 38 is attached to theshaft 31 of the leg assembly 30, and in some examples the attachmentpoint of the stem 38 to the shaft 31 may be varied so as to permitadjustment of the overall height of the leg assembly 30, and thus of thesolar tracking units 200 when mounted thereon. The stem 38 and platemember 39 may have alternate configurations than that described herein.In some examples, a spike member or other attachment component, notshown, for anchoring the leg assembly in the ground and/or electricallygrounding the frame 10 can be provided in addition to or instead ofplate member 39. A distal end of the leg assembly 30 provides a mountingend 35 for mounting an armature assembly bearing the solar trackingmodule 200.

The trusses 12, 22 and leg assemblies 30, and their respectivecomponents, may be manufactured from any suitable material. For example,the trusses and leg assemblies may be manufactured from galvanized steelor aluminum, and may be manufactured from extruded or drawn metaltubing, whether open or seamed. Further, in some examples, at least theupper chord members 14, 24 may be provided with an axial borehole orotherwise formed with an interior channel running the length of thechord member, open at either end (not shown), which is convenientlyprovided when the chord members are manufactured from tubing. Cables,wires and hoses, such as electrical cables and the like, as well as airor water hoses, may be threaded through the upper chord members 14, 24and/or lower chord members 16, 26. Similarly, the leg assembly 30 may beprovided with a similar axial borehole or interior channel. In theexamples illustrated herein, the leg assembly 30 is a tubular member.

FIG. 3 illustrates three trusses 22, 12, 12 of the frame 10 joined tothe four leg assemblies 30 illustrated in FIG. 2. In this example, thethree trusses are assembled with the leg assemblies 30 in a collapsedstate suitable for transportation. In this configuration, the trussesremain joined, but more easily transportable than when the frame 10 iscompletely assembled. The remaining fourth truss 22 may be providedseparately. It will be appreciated, however, that even with the fourthtruss connected in the frame 10, the frame 10 may still be collapsed toa substantially flat, folded structure suitable for transport. This viewillustrates flange units 32, 33, 34 on the leg assemblies 30, which areprovided for mounting the trusses 12, 22. It can be seen from thecollapsed state that the fastening means used to join the trusses 12, 22to the leg assemblies 30, shown in FIG. 4, are advantageously adapted toprovide a hinged connection between each truss 12, 22 and the legassembly 30 to permit the frame 10 to be shipped in a partiallyassembled state. Further, since the trusses 12, 22 may carry cables,wires or hoses in their respective upper or lower chords 14, 16, 24, 26,these components may be pre-threaded through the chords prior toshipping to minimize assembly time in the field, as well as shield thewiring, etc. from the elements, and reducing the need for expensiveconnectors.

Turning to FIG. 4, a further view of the leg assembly 30 is shown. Afirst, lower flange unit 32 is provided near a first end (i.e., near theend joined to the foot member 37) of the leg assembly. The flange unit32 in this example comprises a set of four flanges 32 a, 32 b, 32 c, 32d extending from the leg assembly. In this example of a box frame 10,the flanges 32 a, 32 b, 32 c, 32 d extend radially and are substantiallyequally spaced around the leg assembly 30, i.e., at right angles to oneanother. In this example, the individual flanges 32 a, 32 b, 32 c, 32 dand the lower chord members 16, 26 are provided with correspondingboreholes for receiving fasteners 42. The lower chord member 16, 26 isplaced on the corresponding flange 32 c, 32 b such that the boreholesprovided in each component are substantially aligned, and the fasteners42 are used to join the chord member to its respective flange. Thefasteners 42 may also facilitate an electrical connection between thechord member and the leg assembly 30 via its respective flange forelectrical grounding purposes. Suitable fasteners 42 may be selected forjoining and/or electrically connecting the chord members and flanges,such as the illustrated threaded bolts and washers. The fastenersmentioned herein may, for example, be self-tapping screws or split pins;thus the boreholes in the flange unit 32 and trusses 12, 22 need not bethreaded.

It will be appreciated that other means of attaching a truss 12, 22 tothe leg assembly 30 may be used; for example, the leg assembly 30 neednot be provided with the flange units 32, 33, 34, but instead the upperand lower chords 14, 24, 16, 26 may be directly mounted onto the shaft.The individual flanges 32 b, 32 c, however, also provide support to thelower chord member 26, 16 of the truss 22, 12 mounted thereon. Althoughas illustrated in FIG. 4, the flange units 32, 33, 34 are shown fixed inpredetermined positions on the shaft 31 of the leg assembly 30, in someexamples the flange units 32, 33, 34 may be mounted on the shaft 31 atdifferent heights of the shaft 31. The flange unit 32, for example, maycomprise a tubular body with the flanges 32 a, 32 b, 32 c, 32 dextending therefrom, the tubular body having inner dimensions greaterthan the outer dimensions of the shaft 31. If the shaft 31 and tubularbody of the flange unit 32 are circular, the flange unit 32 may berotated to the desired orientation. The flange unit 32 may be slid alongthe length of the shaft 31 then fixed in position using appropriatefasteners. To simplify field installation, however, the flange units arefixed at predetermined positions.

Once the frame 10 is assembled, two of the flanges 32 a, 32 d in thisexample are not used to join any truss 12 or 22. However, it will beappreciated that providing the additional flanges 32 a, 32 d permits theleg assembly 30 to be joined to additional trusses (not shown), and tospacing arms, described below with reference to FIG. 13.

The upper flange units 33, 34 may be configured in a manner similar tothe lower flange unit 32 described above. The upper flange units 33, 34are spaced from the lower flange unit 32 on the shaft 31 to receive theupper chord members 14, 24 of the trusses 12, 22, again, in a similarmanner to the lower flange unit 32. In this example, the upper chordmembers 14, 24 are disposed between the first flange unit 33, whichsupports the chord member, and the second flange unit 34. Fasteners 44are then used to secure the chord member 14, 24 between the two flanges.

One or more of the leg assemblies 30 can include one or more ports 40positioned at or near a level of the upper chord member 14, 24 when thelatter is mounted to the leg assembly. A single such port 40 is shown inFIG. 4. Cables, wires or hoses threaded through the chord member 14, 24may extend into a first port 40 corresponding to the open end of a firstupper chord member 14, and pass through the leg assembly 30 to emergefrom a second port corresponding to the open end of the second upperchord member 24, through which the cable, wire or hose continues.Alternatively, some cables and wires can be threaded through the chordmember 14, 24 while others are attached to the exterior of the chordmember 14, 24. For example, where the chord member 24 is electricallygrounded, low voltage controls cables can be threaded through the chordmember 14, 24, while high voltage power and controls cables can be runalong the exterior of the chord member 14, 24 in order to electricallyisolate them. In another example, some cables and wires can be attachedto one side of the chord member 14, 24 while others are attached to theother side of the chord member 14, 24 such that the chord member 14, 24acts as an electrical isolator. In yet another example, cables and wiresmay be threaded through the leg assembly 30 and run underground wherethey can be electrically isolated. The leg assembly 30 may also includea separator to isolate high and low voltage cables within the legassembly 30.

The box shape of the example frame 10 provides a sufficiently stableconfiguration for mounting of solar tracking units 200. However, thoseskilled in the art will appreciate that alternative frame configurationsare possible. An example of a triangular frame 50 is shown in FIG. 5, inwhich three trusses 52 are mounted to leg assemblies 54. In thisparticular configuration, the trusses 52 are substantially the samelength, thus yielding a substantially equilateral triangleconfiguration; however, the trusses 52 may include two or threedifferent lengths. The trusses 52 and leg assemblies 54 may be joined ina manner similar to that described in relation to FIG. 4, althoughunlike the example of FIG. 4, the flanges extending from the legassemblies 54 will be arranged at angles suitable for joining thetrusses in the desired triangular configuration.

Two other possible configurations are shown in FIGS. 6 and 7. FIG. 6 isa schematic representation of an X-configuration for a frame 60, withfour trusses 62 mounted to a central support post 66 at a central point,and four leg assemblies 64 joined to a distal end of each truss 62.Solar tracking units, not shown, would then be mounted at least on oneof the leg assemblies 64. The arrangement of the solar tracking units isthus similar to the arrangement of the solar tracking units 200 on thebox frame 10 of FIG. 1. FIG. 7 shows a further X-configuration in whichthe trusses 72 again are mounted to a central support post 76, andextend in a similar arrangement to that shown in FIG. 6; however, thedistal end of each truss 72 is mounted at a distal support post 74, andtwo leg assemblies 78 are joined to each of the distal support posts 74by means of support beams 77 or a further truss. As in the example ofFIG. 6, the frame 70 can support at least four solar tracking units (notshown), which can be mounted on the distal support posts 74. Theexamples shown in FIGS. 6 and 7 can be collapsed to facilitatetransportation. The central support posts 66, 76 are provided withhinged connections, such that the trusses 62, 72 can be rotated. Thedistal support posts 74 of FIG. 7 are also provided with hinges, suchthat the leg assemblies 78 can be collapsed.

In the example illustrated in FIG. 1, the solar tracking units 200 aremounted on a mounting end 35 of the leg assemblies 30. The solartracking unit 200 includes an armature assembly 80, shown in FIG. 8. Asolar panel, such as those described in further detail below withreference to FIGS. 9 and 10, may be mounted on each of the armatureassemblies 80. Each solar tracking unit 200 can also be provided with asun position sensor (not shown) for use in computerized calibration toensure that sunlight is normally incident on the surface of the solarpanel, and to compensate for the vagaries of the field installation suchas uneven terrain affecting the pitch of a given unit 200, and otherissues such as manufacturing errors in the manufacture of the solarpanel 210, 220 or its components, differences between the actual sunposition and expected sun position, and the like.

The armature assembly 80 includes a shaft 82 having an external diametersized to fit within the mounting end 35 of the leg assembly 30. Theorientation of the shaft 82 within the leg assembly 30 may be determinedduring field installation, but generally the orientation will bedetermined by the desired north-south alignment of the frame 10 and thesolar tracking units 200. Alignment of the solar tracking unit 200 onthe frame 10 can be set by one or more notches or embrasures 93 at thefirst end of the shaft 82′, which receive one or more correspondingprotrusions or pins (not shown) within the mounting end 35 of the legassembly 30. In the example of FIG. 8, a first collar 98 and a secondcollar 99 are provided on the shaft 82 set back from the first end 82′.Each of the first and second collar 98, 99 have an external diametergreater than the shaft 82 or first end 82′, with the first collar 98being sized to fit within the mounting end 35 of the leg assembly 30(not shown in FIG. 8) with minimal or no clearance. The second collar 99can have substantially the same external diameter as the first collar 98so as to similarly fit within mounting end 35, with an upper lip 81 ofgreater diameter, which rests on the top edge of the mounting end 35 ofthe leg assembly 30 when mounted. Thus, the position of the lip 81 onthe shaft 82, and in some examples the depth of the notches 93,determine the height of the armature assembly 80 once mounted on the legassembly 30. In other examples, the entirety of the second collar 99 canhave an external diameter greater than at least the internal diameter ofthe mounting end 35 of the leg assembly 30, and the lip 81 may beeliminated. The second collar 99 in that case would rest on the top edgeof the mounting end 35. When mounted, the shaft 82 can be furthersecured to the mounting end 35 with flats 94 or other receptacles (forexample, bores or other apertures) adapted to receive fasteners (forexample, set screws, not shown) provided in the mounting end 35. In someexamples, bores 36 (shown in FIG. 4) are provided in the mounting end 35for receiving the fasteners.

The armature assembly includes a yoke 84 provided with a yoke mount 79,a crosspiece 85 extending from the yoke mount 79, and first and secondarms 86 extending from the crosspiece 85. In the configuration shown inFIG. 8, the arms 86 extend substantially perpendicularly from thecrosspiece 85 and are substantially parallel to the yoke mount 79 and toeach other, although in other configurations their relative positionwith respect to the crosspiece 85 and the yoke mount 79 may varyaccording to the design of the solar panel mounted on the armatureassembly 80. A gusset 83 for added rigidity is mounted on the crosspiece85 and arms 86. The yoke mount 79 extends through and is fixed to thecenter of crosspiece 85. The yoke mount 79, the crosspiece 85, the arms86 and the gusset 83 may be manufactured as individual components weldedtogether to form the yoke 84. Alternatively, the yoke 84 may beintegrally formed as a single part by die casting.

A bearing or bushing, not shown in FIG. 8, may be provided within theyoke mount 79 to facilitate rotation of the yoke 84 about shaft 82. Afirst drive system for controlling yaw movement of the solar trackingunit 200 includes a first gear wheel 90 fixed to the shaft 82, andtherefore stationary relative to the frame 10. A second gear wheel 91 inengagement with the first gear wheel 90 is also provided on thecrosspiece 85, extending from the same face of the crosspiece 85 as thefirst gear wheel 90. The second gear wheel 91 is fixed relative to theyoke 84. In the example of FIG. 8, the first and second gear wheels 90,91 are disposed on the inside of the yoke 84, i.e., between the arms 86.A first drive assembly including a motor and gearbox 92 is provided forthe second gear wheel 91 for controlling rotation of the second gearwheel 91 to cause the yoke 84 to rotate around the fixed first gearwheel 90 and the shaft 82. An example of a suitable drive assemblyincludes a weatherproof and durable stepper motor having an output shaftconnected to a sealed gearbox that has an output shaft with a piniongear (the second gear wheel 91). The pinion gear (the second gear wheel91) can therefore provide higher torque than the stepper motor, theincrease in torque depending on the gear ratios of the gears containedinside the sealed gearbox. The pinion gear connected to the output shaftof the sealed gearbox engages the first gear wheel 90 and can operate inan unsealed environment. The first drive system thus provides forrotation of the yoke 84 up to 360 degrees (or greater) in a clockwise orcounter-clockwise direction. In use, the armature assembly 80 may beenclosed in a weatherproof cover (not shown) to protect the drivesystems from ice, rain, sand, etc.

An axle 88 is mounted through holes 87 provided near the ends of the twoarms 86. Again, appropriate bearings or bushings may be provided, notshown. Each end of the axle 88 terminates in a plate 89 for mounting toan underside of a solar panel, shown in the following figures. Theprecise configuration of the plates 89 will depend on the attachmentmeans used to mount the solar panel to the armature assembly 80; in thiscase, grooves are provided in the perimeter of the plate 89 to receivefasteners to join the armature assembly 80 to the solar panel. A seconddrive system controlling pitch of the solar tracking unit 200 isprovided on the yoke 84 and axle 88; a first gear wheel 95 is mounted onthe axle 88, and a second gear wheel 96 in engagement with the firstgear wheel 95 is mounted on the yoke 84. In this example, the first gearwheel 95 is a circular sector wheel rather than a full circle like thegear wheel 90. Since yaw over a wider range (i.e., over 180 degrees) maybe provided by the first drive assembly comprising the gear wheels 90,91, pitch adjustment of the solar tracking unit 200 over a range of 90degrees is likely sufficient. In other examples, the gear wheel 95 maybe a semicircular shape rather than a quarter-wheel; depending on theproximity of the solar panel to the axle 88, it may not be possible toprovide a full-circular gear wheel on the axle 88. The second gear wheel96 is controlled by a further drive system including a motor and gearbox97, also mounted on the yoke 84. An example of a suitable drive assemblyincludes a weatherproof and durable stepper motor having an output shaftconnected to a sealed gearbox that has an output shaft with a piniongear (the second gear wheel 96). The pinion gear (the second gear wheel96) can therefore provide higher torque than the stepper motor, theincrease in torque depending on the gear ratios of the gears containedinside the sealed gearbox. The pinion gear connected to the output shaftof the sealed gearbox engages the first gear wheel 95 and can operate inan unsealed environment. In the example of FIG. 8, the motor 97 andsecond gear wheel 96 are mounted on the arm 86 proximate to the gearwheel 95.

In FIG. 8, spur gears are illustrated; however, other types of gears maybe employed as well to provide motion in the two substantiallyorthogonal planes perpendicular to the shaft 82 and axle 88. Tensionsprings, not shown, may be provided to ensure engagement between theteeth of the gears 91, 96 and 90, 95. Home switches, not shown, may beprovided on each of the two drive assemblies for use in returning thesolar panels to a default position. Both the motors 92 and 97 arecontrollable using a local control unit described below.

The solar panel mounted to the armature assembly 80 may take anysuitable shape. For example, the solar panel can include one or moreflat plate solar panel modules made of semiconductors such as silicon,gallium arsenide, cadmium telluride, or copper indium gallium arsenideor can be a concentrated solar panel employing concentrating optics. Inthe case of concentrated solar panels, the solar panels includeindividual optical modules comprising PV cells. The optical modules mayor may not include integrated electronics such as power efficiencyoptimizers and the like. Optics provided with the individual opticalmodules may include multiple-component optics. Embodiments ofmultiple-optic assemblies are described in United States PatentApplication Publication Nos. 2011/0011449 filed 12 Feb. 2010 and2008/0271776 filed 1 May 2008. An integrated concentrating PV module isdescribed in United States Patent Application Publication No.2011/0273020 filed 1 Apr. 2011. The entireties of the documentsmentioned herein are incorporated herein by reference. The individualoptical modules may be combined in series in strings of optical modules,which in turn may be connected in parallel with other strings to yieldan array of optical modules. One or more strings of optical modules canbe arranged in a plane to form a solar panel module.

FIG. 9 illustrates a first solar panel 210 in a “podium” configuration,in which solar panel modules of optical modules are arranged in astaggered formation to define a two-level panel. Strings of opticalmodules are mounted on one or more crosspieces 212 to form the solarpanel modules. The crosspieces 212 may be manufactured from aluminum orany suitable material providing the weather resistance, rigidity andstability required for field use. The crosspiece 212 defines at leastone recessed level 213 and at least one raised level 214, each bearing aplurality of optical modules 218. The crosspiece 212 in FIG. 9 comprisesa single raised level 214 between two recessed levels 213; however,multiple raised levels 214 may be interleaved between multiple recessedlevels. In this example, the optical modules 218 are mounted on heatsinks 216 which space the optical modules 218 from the crosspiece 212.Heat sinks may be manufactured from any suitable material; in FIG. 9,the heat sinks 216 are manufactured from extruded aluminum, and have an“I” beam configuration including a support 216 a, which is mounted tothe crosspiece 212 such that the optical modules 218 are substantiallyparallel to the level 213, 214, and the set of optical modules on agiven level 213, 214 are substantially flush with one another. A seriesof fins 216 b are provided to dissipate heat. Multiple crosspieces 212to which the optical module strings are fixed are themselves connectedby beams 215, shown in FIGS. 11 and 12, to which the armature assembly80 can be attached.

An alternative “delta” solar panel configuration 220 is shown in FIG.10. In this example, the crosspiece 222 comprises two arms 224 angledand meeting at a central apex 226. Again, the optical modules 230 aremounted to heat sinks 228, which in turn are mounted to the arms 224 atsupports 228 a. While, as mentioned above with respect to FIG. 9, theheat sinks may take a different form, the modified “I” beam form shownin FIG. 10 permits the individual optical modules 230 to be mountedparallel to each other in a terraced arrangement. Again, the armatureassembly 80 can be mounted to beams, not shown in FIG. 10. Both thesestaggered and delta configurations 210, 220 thus offset adjacent stringsof optical modules at different heights and consequently improve airflow around the panel, thus assisting in reducing wind loading andpromoting thermal transfer from the heat sinks, and may allow the panels210, 220 to operate at a somewhat higher efficiency than otherwise. Asolar panel comprising a plurality of flat plate solar panel modules canlikewise have a staggered or a delta configuration. In some examples,solar panel modules can be attached directly onto the at least onerecessed level 213 and the at least one raised level 214 or onto theangled arms 224, without the need for heat sinks 216, 228.

FIG. 11 illustrates the connection of the crosspieces 212 and beams 215mentioned above. The plates 89 provided on the axle 88 of the armatureassembly 80 may be fixed to the beams 215 using appropriate fasteningmeans. The individual solar tracking units 200 and panels are usefullymounted with their center of gravity aligned with the position of theleg assembly 30 to enhance stability of the unit overall. The staggeredand delta configurations of the solar panels 210 and 220 also enhancestability once installed; when the panels are mounted on the armatureassembly 80, the axis of rotation (the pitch rotation, as defined by theaxle 88) is substantially aligned with the center of gravity of thepanel 210, 220 due to the arrangement of the offset adjacent strings ofoptical modules. This can be seen in FIGS. 9 and 10 by the position ofthe axle 88 with respect to the panel 210, 220. The panel design thusreduces the amount of energy required to drive the panel betweendifferent orientations, and assists in maintaining tracking accuracy.

Alternatively, the solar panel, whether a flat plate solar panel or asolar panel comprising concentrating optics, may have a “planar” solarpanel configuration where all the receivers lie in one plane (notshown). If the center of gravity of the solar panel and panel frame usedto mount the solar panel to the armature assembly is not at the centerof the axle 88, then when the axle 88 is rotated, the center of gravitywill be moved vertically against gravity requiring the system to dowork. Therefore it can be advantageous to maintain the center of gravityof the solar panel and panel frame at the center of the axle 88. Tomaintain the center of gravity of the solar panel and panel frame at thecenter of the axle 88 a counterweight may be attached to the solar panelor panel frame to shift the center of gravity to the desired location(not shown).

FIG. 11 also illustrates a possible conduction path for grounding thesupporting structures of the solar tracking units 200. A conductor 1100is fixed at or near one end by a fastener 1101 to the beam 215, andextends to the fastener 1103 affixing the conductor 1100 to the gusset83. A second end of the conductor 1100 is then fixed to the mounting end35 of the leg assembly 30, for example at a further fastener 1105joining the armature assembly 80 to the leg assembly 30. The conductor1100 is fastened to the armature assembly 80 allowing enough slack topermit movement of the solar tracking unit 200 using the yaw and pitchdrive assemblies. The conductor 1100 may be any suitable grounding wireor cable, such as insulated 10-gauge wire, and the fasteners anysuitable type, and are advantageously self-tapping ground screws thatare corrosive-resistant and paint-coated to resist degradation in fieldconditions.

FIG. 12 illustrates an alternate wiring for grounding the supportingstructures of the solar tracking unit 200. In this example, a firstlength of conductor 1201 is fixed between the fastener 1101 and afurther fastener 1102 provided on the yoke arm 86. A second length ofconductor 1202 is fastened to the gusset 83 using fastener 1103, and tothe leg assembly 30 by the fastener 1105 on. In this manner, the yoke 84and the gusset 83 provide part of the conductive grounding path, ratherthan relying on a longer length of cabling to provide the conductivepath. In this manner, the amount of torsion and/or bending of the cablemay be reduced, compared to the wiring of FIG. 11, since the conductor1201, 1202 is subjected to less movement as the yaw and pitch driveassemblies move the solar tracking unit 200 along multiple axes.

When deployed in the field, box frames 10 are advantageously positionedso that one truss of the frame 10 is aligned in a north-south direction.An example of alignment and positioning is shown in FIG. 13, whichdepicts three box frames 10 as they may be arranged in the field withshorter trusses oriented in a north-south direction. To maintain spacingbetween the frames 10, spacing arms 1302, 1304 of predetermined lengthare fixed to trusses or leg assemblies of adjacent frames 10. Spacingarms 1302, 1304 may be aligned with upper chord members 14, 24 or alongthe ground. For example, as illustrated in FIG. 13, spacing arms 1302oriented in the north-south direction can be aligned with upper chordmembers 14, 24 and spacing arms 1304 oriented in the east-west directioncan be at or near ground level which can allow for people to move moreeasily between the frames 10 and, where spacing permits, for vehicles tobe driven between the frames 10 in the east-west direction. Theinterconnection enhances the structural solidity of the frames 10overall, and reduces the need for external ballasting of the frames 10.The lengths of the spacing arms 1302, 1304 and the dimensions of theframes 10 themselves are selected according to the desired spacing ofindividual solar tracking units 200, which can be based at least in parton the size of the solar panels and/or environmental considerations suchas shading and wind speeds, and on manufacturing considerations, forexample based on an analysis of the relative component, shipping andland use costs and optimal power production. For example, the distancebetween leg assemblies in the north-south direction may be approximately3.44 m and the distance between leg assemblies in the east-westdirection may be approximately 4.98 m where panels of the type shown inFIGS. 11 and 12 are used.

In addition to physical interconnection of frames 10 of the solartracker assemblies 100 for the purpose of enhancing stability, theindividual solar tracking units 200 are interconnected within a singlesolar tracker assembly 100. A local control unit 1402 (LCU), shown inFIG. 14, can be provided on each assembly 100 to control all solar units200 provided on a single frame 10. Alternatively, a single LCU 1402 canbe used to control the solar tracking units 200 on several frames (notshown). For example, a cluster of frames 10 could be positioned andarranged such that an LCU 1402 is mounted only to a single frame 10 ofthe cluster and the other frames 10 do not have local control unitsmounted thereto. Wires can be run from the single LCU 1402 to each ofthe solar tracking units 200 on the frames of the cluster. Within agiven frame 10 having four solar tracking units 200, pairs of the units200 may be connected in series with one another, and these pairsconnected in parallel with one another, thus permitting increasedvoltage to reduce power losses in interconnecting wires. Each pair ofunits 200 can be provided with a current and/or voltage sensor (notshown) in communication with the LCU 1402. In some examples, individualsolar tracking units 200 on a single frame are independentlycontrollable and each solar tracking unit 200 can be provided with acurrent and/or voltage sensor.

The LCU 1402 can receive input including astronomical data (which may bepre-programmed in the LCU or alternatively received over a network),readings from the current or power sensors, and readings from the sunposition sensors on each solar tracking unit 200. The LCU uses the inputdata to determine the solar panel position for each unit 200 and outputssignals to control the motor and to communicate with other components inthe field or over a network. The LCU 1402 may also be provided with atemperature sensor to measure the ambient temperature at the assembly100 site. If the temperature is detected to rise above a predeterminedthreshold, the LCU 1402 can stop tracking the sun until the temperaturereturns to an operational range (e.g., −20 to +50 degrees Celsius). Ifwind speed exceeds a predetermined threshold (e.g., over 35 mph), theLCU 1402 can output a signal to the motors 92, 97 to move the solartracking units 200 into a horizontal “stowed” position. If notemperature (or wind speed) sensor is provided on the individualassembly 100, weather data may be provided to the LCU 1402 over acommunication line from a central location in a solar farm in which theassembly 100 is located, or alternatively from another network source.

The LCU 1402 may self-calibrate its expected sun position determinedfrom received astrological data by comparing feedback from the sunsensors or power sensor (i.e., current and/or voltage sensors) on eachtracking unit 200 in the iterative process shown in FIG. 15. At 1510, aninitial sun position is calculated by the LCU 1402. At 1520, feedback isreceived from the sun sensors, and at 1530 an offset is computed betweenthe received sun sensor data and the calculated position. An orientationdifference between the feedback position and the calculated position isdetermined at 1540, and at 1550 a coordinate transformation based onthat determined difference is applied to the calculated position. As theLCU 1402 continues to receive feedback from the sensors at 1520, thetransformation may be further adjusted. The transformation is thenapplied to other sun position calculations made by the LCU 1402 tocontrol the position of the solar panels 210, 220 on the various solartracking units 200. While the sun sensors on each solar tracking unit200 thus may be used to compensate for factors such as uneven terrain orimperfect installation, misalignment of the sun sensor with respect tothe individual panel 210, 220 in the unit 200 may result in continuousdegraded performance. Accordingly, the LCU 1402 may additionally oralternatively track the mechanical maximum power point (MPP) for eachpanel or plurality of panels using the current and/or voltage sensors,and carry out calibration of the panels by incrementally adjusting thealignment of individual panels along each axis to determine an optimalposition.

Multiple LCUs 1402 can be interconnected in the field by field wiring1400, as shown in FIG. 14. The field wiring 1400 may include a power busfor the assemblies 100 as well as communication wiring for each of theLCUs 1402. In one example, power line communication is used to effectcommunication between the LCUs 1402 and a global control or supervisoryunit, not shown, which receives data from each of the plurality of LCUs1402 within a farm or sub-farm of assemblies 100. The global controlunit may receive data such as sun sensor data, power or current readingsfor each individual tracking unit 200 pair or for the entire assembly100, and may transmit data to the LCUs 1402 including motor controlinstructions and other operational data, such as astrological data.Control of individual solar tracking units 200 may also be effected fromthe global control unit, thus overriding the associated LCU 1402. Forexample, maintenance personnel may use the global control unit to forcethe solar tracking units 200 the stowed position or to another positionfor maintenance and repair, or to deactivate single solar tracking units200. In other examples, wireless (RF) communication or wired serialcommunications may be used between the LCUs 1402 and the global controlunit. The global control unit may also optionally be accessible byoperators over a public or private network, such as the Internet, forremote control of the global control unit and of individual LCUs 1402.There is thus provided a network of independently operable solartracking units 200, each of which may be controlled using a centralcontrol system.

Some or all of the LCUs 1402 can also be made so that they do notrequire field wiring. This can be achieved by using wireless (e.g.,radio frequency) communication between the LCUs 1402 and the globalcontrol unit and by powering the LCUs 1402 either off the solar panelsthat the LCU is tracking or by powering each of the LCUs 1402 with oneor more secondary solar panels that are connected directly to the LCU1402 and do not contribute to the power conducted by the main power busof the solar farm which conducts the power produced by the solartracking units 200. The secondary solar panels can be integrateddirectly into the casing of the LCU 1402 (not shown).

The global control or supervisory unit can be integrated into one of theLCUs 1402 in a solar farm. Alternatively a smaller solar farm might needonly a single LCU controlling multiple trackers and servingsimultaneously as the LCU and the global control unit.

FIG. 16 illustrates an example layout of a solar sub-farm or assemblyarray 1600 using solar tracking assemblies 100 a-100 i as describedherein. The array 1600 in FIG. 16 includes nine assemblies 100 set outin a grid formation, with columns of assemblies 100 connected by spacingarms 1602, 1604 and field wiring, which may follow the path of thespacing arms 1602, 1604. It can be seen that assemblies 100 e and 100 fdo not include a full complement of solar tracking units 200.

Typically, when assemblies 100 are installed, the supporting structuresof each solar tracking unit 200 is grounded using the conductive pathsdescribed above with respect to FIGS. 11 and 12. An earthing electrodesuch as a grounding rod or spike may be connected to each of the legassemblies 30 to prevent the accumulation of undesired voltage on theframes 10 and the supporting structures (e.g. the crosspieces, beams andarmature assembly) of the solar tracking units 200. To reduce cost ofinstallation, since the spacing arms 1602, 1604 provide a conductivepath between the units 200, a central grounding location for a groundingrod or spike 1650 connected to one of the frames 10 of the assemblyarray 1600 is selected in a position that provides the minimum possiblepath between the furthest individual solar tracking unit 200 within thearray 1600 and the grounding spike 1650.

With the foregoing frame 10 and units 200, the solar tracker assemblies100 are easily installed in the field. As mentioned above, variousfeatures of the assemblies 100 can compensate for uneven terrain;advantageously rough grading of the site is carried out to roughly levelthe ground, and to create paths for maintenance access. On unstableground or fertile soil, a thin layer of crushed concrete aggregate maybe distributed to assist in stabilizing the ground and/or prohibitingplant grown. The pre-wired, collapsed frame 10 having three trusses 12,22 is unfolded, and the fourth truss 22, 12 fixed in place. The footmember 37 on each leg assembly 30 is adjusted, if necessary, tocompensate for uneven terrain; however, this adjustment need not becompletely accurate since variations in the terrain can also becompensated for by auto-calibration of the tracker modules. Armatureassemblies 80 are then distributed to each leg assembly 30, and droppedinto place on the mounting end 35 of the leg assembly 30, and fixed inplace with a fastener. The solar panel 210, 220 is then fixed to thearmature assembly 80 via the plates 89 and fasteners. The overall heightof the frame 10 and armature assembly 80 is such that cranes or similarequipment are not necessary for installation of the panels 210, 220. Ina further embodiment, the panels 210, 220 are shipped with removablehandles that permit the installation personnel to lift the solar panel210, 220 and to place it on the armature assembly 80.

Grounding wires are then attached as necessary, and the motors 92, 97connected to wiring within the frame 10 leading to the local controlunit 1402. The motor wiring may pass, in part, through the legassemblies 30 and/or truss assemblies. The local control unit 1402 ismounted on the frame 10 and connected to the wiring already provided onthe frame 10. The local control unit 1402 is then connected to the powerbus interconnecting the other assemblies 100. Field wiring is providedby pre-cut and terminated bundles of PV-rated cabling containing the PVpower bus and the local control unit power/communication bus. The fieldwiring may lie directly on the ground between solar tracker assemblies100, although in those regions where it may interfere with maintenancepaths between assemblies 100 it may be desirable to bury the cabling orotherwise protect it.

If air or water hosing is provided within the frame 10, this hosing isconnected to a source. The hosing may be connected to cleaningimplements (e.g., a spray gun) and used to clean the tracking solarmodule 200 or other components of the assembly 100.

Another configuration of a solar tracker assembly or unit 2100 is shownFIG. 17. The assembly 2100 generally includes a ground-mounted frame2010 for supporting one or more solar tracking units 2200, which caninclude PV tracker modules as described above, or heliostat mirrors. Inthe example illustrated in FIG. 17, the solar tracking units 2200 areshown supporting a solar panel module 2210 with several solar panels2205. The frame 2010 includes a plurality of trusses 2012 ofsubstantially equal length. The assembly of the trusses 2012 yields anoverall parallelogrammatic, and in this specific example, a rhombus (ordiamond) frame 2010. The sides of the frame 2010 need not employ trussesspecifically, although the benefits of the structural stability of atruss design will be appreciated by those skilled in the art.

Each individual truss 2012 includes an upper chord member 2014 and lowerchord member 2016. The chord members 2014 and 2016 are joined by a setof truss members 2017. Trusses 2012 in this example each include a setof four truss members 2017. The selection and arrangement of the trussmembers 2017 need not be limited to the example shown; depending on theselected dimensions and materials of the frame 2010, more or fewer trussmembers 2017 may be employed. In addition, one or more struts 2018 maybe mounted between the upper and lower chord members 2014 and 2016 toprovide additional vertical support between the chord members. In theexample of FIG. 18 two struts 2018 are provided between adjacent trussesand these can be used to support the LCU 2402.

The trusses 2012 are joined at or near their respective ends at legassemblies 2030 shown in further detail in FIG. 19A. A cross member 2046attaches the two leg assemblies 2030 a, 2030 c that are positionedclosest to one another, and adds structural support and rigidity.Additional truss members 2048 extending from the trusses 2012 to thecross member 2046, which here is depicted as a chord member that can bemanufactured in a similar manner to the chord members and leg assembliesof the frame, and can also be a truss, also add structural support. Eachleg assembly 2030 includes a shaft 2031, and can include an adjustablefoot member 2037. The foot member 2037 in this example is detachable andincludes a plate member 2039 extending from a stem 2038. The stem 2038is attached to the shaft 2031 of the leg assembly 2030, and in someexamples the attachment point of the stem 2038 to the shaft 2031 may bevaried so as to permit adjustment of the overall height of the legassembly 2030, and thus of the solar tracking units 2200 when mountedthereon. The stem 2038 and plate member 2039 may have alternateconfigurations than that described herein. In some examples, a spikemember or other attachment component, not shown, for anchoring the legassembly in the ground and/or electrically grounding the frame 2010 canbe provided in addition to or instead of plate member 2039. A distal endof the leg assembly 2030 provides a mounting end 2035 for mounting anarmature assembly 2080 for bearing the solar tracking module 2200.

The trusses 2012 and leg assemblies 2030, and their respectivecomponents, may be manufactured from any suitable material. For example,the trusses and leg assemblies may be manufactured from galvanized steelor aluminum, and may be manufactured from extruded or drawn metaltubing, whether open or seamed. Further, in some examples, at least theupper chord members 2014 may be provided with an axial borehole orotherwise formed with an interior channel running the length of thechord member, open at either end (not shown), which is convenientlyprovided when the chord members are manufactured from tubing. Cables,wires and hoses, such as electrical cables and the like, as well as airor water hoses, may be threaded through the upper chord members 2014and/or lower chord members 2016. Similarly, the leg assembly 2030 may beprovided with a similar axial borehole or interior channel. In theexamples illustrated herein, the leg assembly 2030 is a tubular member.

Six brackets 2049 extend from the leg assembly 2030 shown in the exampleof FIG. 19A. Each of the brackets 2049 are provided with boreholes forreceiving fasteners 2042. The lower chord members 2016 are placed on thecorresponding brackets 2049 e and 2049 f such that the boreholesprovided in each component are substantially aligned, and the fasteners2042 are used to join the chord member to its respective bracket. Theupper chord members 2014 are sandwiched between two brackets 2049 a,2049 c and 2049 b, 2049 d respectively, the extra brackets provideadditional support. The fasteners 2042 may also facilitate an electricalconnection between the chord member and the leg assembly 2030 via itsrespective bracket for electrical grounding purposes. Suitable fasteners2042 may be selected for joining and/or electrically connecting thechord members and brackets, such as the illustrated threaded bolts andwashers. The fasteners mentioned herein may, for example, beself-tapping screws or split pins; thus the boreholes in the brackets2049 and trusses 2012 need not be threaded.

It will be appreciated that other means of attaching a truss 2012 to theleg assembly 2030 may be used; for example, the leg assembly 2030 neednot be provided with the brackets 2049, but instead the upper and lowerchords 2014, 2016 may be directly mounted onto the shaft. The individualbrackets 2049, however, also provide support to the chord member 2014,2016 mounted thereon.

Although as illustrated in FIG. 19A, the brackets 2049 are shown fixedin predetermined positions on the shaft 2031 of the leg assembly 2030,in some examples the brackets 2049 may be mounted on the shaft 2031 atdifferent heights of the shaft 2031.

The shaft 2031 and the plate member 2039 are provided with additionalboreholes. It will be appreciated that providing the additionalboreholes permits the leg assembly 2030 to be joined to additionaltrusses (not shown), and to spacing arms. With reference to FIG. 19B, itis shown that a spacing arm 2304 can be mounted to the leg assembly 2030by means of mounting features in the spacing arm 2304 provided withboreholes, such as the illustrated fork 2343, fixed to the leg assembly2030 by fasteners (not shown). With reference to FIG. 19C, it is shownthat a spacing arm 2302 can be assembled onto the plate 2039 by means ofboreholes and fasteners. One or more of the leg assemblies 2030 caninclude one or more ports 2040 positioned at or near a level of theupper chord member 2014 when the latter is mounted to the leg assembly.A single such port 2040 is shown in FIG. 19A. Cables 2054, wires orhoses threaded through the chord member 2014 may extend into a firstport 2040 corresponding to the open end of a first upper chord member2014, and pass through the leg assembly 2030 to emerge from a secondport corresponding to the open end of the second upper chord member2014, through which the cable, wire or hose continues. Alternatively,some cables and wires can be threaded through the chord member 2014while others are attached to the exterior of the chord member 2014. Forexample, where the chord member 2014 is electrically grounded, lowvoltage controls cables can be threaded through the chord member 2014while high voltage power and controls cables can be run along theexterior of the chord member 2014 in order to electrically isolate them.

In another example, some cables and wires can be attached to one side ofthe chord member 2014 while others are attached to the other side of thechord member 2014 such that the chord member 2014 acts as an electricalisolator. In yet another example, cables and wires may be threadedthrough the leg assembly 2030 and run underground where they can beelectrically isolated. The leg assembly 2030 may also include aseparator to isolate high and low voltage cables within the leg assembly2030. The mounting end 2035 of the leg assembly includes an upper lip2043 provided with fasteners 2045 for coupling and fastening an armatureassembly thereto. In this particular example the fasteners 2045 can be,but are not limited to press fitted wheel studs for fastening anarmature by means of nuts.

FIG. 20 illustrates four trusses 2012 of the frame 2010 joined to thefour leg assemblies 2030. In this example, the four trusses areassembled with the leg assemblies 2030 in a collapsed state suitable fortransportation. In this configuration, the trusses remain joined, butmore easily transportable than when the frame 2010 is completelyassembled. This view illustrates brackets 2049 on the leg assemblies2030, which are provided for mounting the trusses 2012. The brackets2049 can be welded onto the leg assembly 2330, or attached by any othermeans. It can be seen from the collapsed state that the fastening meansused to join the trusses 2012 to the leg assemblies 2030, areadvantageously adapted to provide a hinged connection between each truss2012 and the leg assembly 2030 to permit the frame 2010 to be shipped ina partially assembled state. Further, since the trusses 2012 may carrycables, wires or hoses in their respective upper or lower chords 2014,2016 these components may be pre-threaded through the chords prior toshipping to minimize assembly time in the field, as well as shield thewiring, etc. from the elements, and reducing the need for expensiveconnectors.

As shown in FIG. 21 a frame 2010 can be collapsed by detaching truss2012 b from leg assembly 2030 c and detaching truss 2012 d from legassembly 2030 d. This can be done by removing the fasteners that fastensaid trusses to the respective brackets of said leg assemblies. In thecases where the fasteners are screws and bolts, these can simply beremoved for shipping and reattached during assembly. As described by thearrows, truss 2012 b rotates towards truss 2012 a. Then both trusses2012 a and 2012 b are rotated together towards the cross bar 2046.Further, trusses 2012 c and 2012 d rotate individually towards the crossmember. The result is a collapsed frame as shown in FIG. 20.

As described previously a rhombus-shaped tracker assembly 2100 has twoleg assemblies 2030 a, 2030 c that are closer together and two legassemblies that are further apart 2030 b, 2030 c, as shown in FIGS. 22Aand 22B. FIGS. 22A and 22B are two different side views of the frame2010. Rhombus-shaped tracker assemblies 2100 stagger the position of thesolar tracking units mounted thereto to minimize shading-related losses.

Trackers can be interconnected with pre-measured spacing arms tominimize installation time, as well as optimize field layout for minimaltracker-to-tracker shading. A field of interconnected tracker assemblies2100 can thus mutually ballast each other. In one example, a field ofinterconnected tracker assemblies may enable operation in winds up to 35mph. An example of alignment and positioning is shown in FIG. 23, whichdepicts nine frames 2010 in rows as they may be arranged in the field.When deployed in the field, tracker assemblies 2100 are advantageouslypositioned so that the cross members 2046 are aligned in a north-southdirection. It can be seen from FIG. 23, and from FIG. 24C discussedbelow, that a consequence of such positioning is that adjacent sides ofadjacent frames are substantially parallel, taking into account possiblevariations in terrain. The resultant geometry of the solar trackingunits and frames of these examples will be readily appreciated by thoseskilled in the art. To maintain spacing between the frames 2010, spacingarms 2302, 2304 of predetermined length are fixed to trusses or legassemblies of adjacent frames 10. Spacing arms 2302, 2304 may be alignedwith upper chord members 2012 or along the ground. For example, asillustrated in FIG. 23, spacing arms 2304 can be aligned with upperchord members 2012 and spacing arms 2302 oriented in the north-southdirection can be at or near ground level which can allow for people tomove more easily between the frames 2010 and, where spacing permits, forvehicles to be driven between the frames 2010.

The interconnection enhances the structural solidity of the frames 2010overall, and reduces the need for external ballasting of the frames2010. The lengths of the spacing arms 2302, 2304 and the dimensions ofthe frames 2010 themselves are selected according to the desired spacingof individual solar tracking units 2200, which can be based at least inpart on the size of the solar panels and/or environmental considerationssuch as shading and wind speeds, and on manufacturing considerations,for example based on an analysis of the relative component, shipping andland use costs and optimal power production.

FIGS. 24A-24C further illustrate a possible implementation of a field orfarm of rhombus-shaped tracker assemblies 2100. FIG. 24A is an isometricview of an example tracker assembly 2100 similar to that of FIG. 17.FIG. 24B is a side view, of the example tracker assembly 2100. FIG. 24Cis a top view of an example solar farm similar to that shown in FIG. 23.

As can be seen in FIG. 24A, in the example shown here, the solartracking units 2200 mounted on the frames can accommodate modules 2205of standard-sized silicon PV solar panels 2210. The solar panel modules2205 can be positioned on-sun throughout the day within 2 degrees ofprecision by a field-proven drive train. FIG. 24C illustrates therelative position of solar tracking units (here, with solar panelsmounted on armatures, the latter not being not shown) with respect toone another in an example field of four solar tracker assemblies 2100a-2100 d. Circumference c indicates the range of the panel turningradius on an axis of the solar tracking unit. As already describedabove, structural support and rigidity of each solar tracker assembly2100 a-2100 d can be enhanced by corresponding cross members 2046,indicated in FIG. 24C as 20146 a, 20146 b, and 2046 c in solar trackerassemblies 2100 a, 2100 b, and 2100 c. Also as described above,alignment and positioning can be maintained between the frames byspacing arms 2302, 2304 of predetermined lengths, which are fixed totrusses or leg assemblies of adjacent frames. FIG. 24C illustrates thatframes 2010 a, 2010 b, and 2010 c are interconnected with each other andwith other solar tracker assemblies (not shown) with spacing arms 2302and 2304. As can be seen in FIG. 24C, one spacing arm 2302 can beparallel to the cross members 2046 of the frames 2010, while the otherspacing arm 2304 can be parallel with a side of the frames 2010. Thesespacing arms of predetermined length thus assist in maintaining regularspacing between adjacent frames 2010 and accordingly between adjacentsolar tracking units 2100.

In this example, the distance in the north-south direction between legassemblies, and consequently solar tracking units, is indicated by d₁ inFIG. 24C and is approximately 4.8 m. The distance between leg assembliesin the east-west direction, as indicated by d₂, is approximately 8.083m. It can also be seen in FIG. 24C that the arrangement of theserhombus-shaped frames 2010 a-2010 d results in corresponding pairs ofleg assemblies (not shown in FIG. 24C) spaced by substantially the samedistance, taking into account possible variations due to uneven terrain,although as discussed herein the configuration of the solar trackerassemblies can mitigate such variations. For example, the pair of solartracking units 2201 a and 2203 a, which is the pair of solar trackingunits that are closest together in solar tracking assembly 2100 a, arespaced by distance d₁ along the north-south direction; likewise, thecorresponding pair of solar tracking units 2201 b and 2203 b in adjacentsolar tracking assembly 2100 b is spaced by the same distance d₁. Inaddition, it can be seen in the example of FIG. 24C that the distance inthe same direction between corresponding leg assemblies or solartracking units 2201 a, 2201 b in two adjacent solar tracking assemblies2100 a, 2100 b is also d₁. Similarly, FIG. 24C further illustrates thatthe distance between the remaining pair of solar tracking units or legassemblies in a given solar tracking assembly (e.g., solar trackingunits 2204 a and 2202 a of assembly 2500 a), indicated as d₂, is thesame as the distance between corresponding solar tracking units or legassemblies in adjacent solar tracking assemblies, as can be seen by thedistance d₂ in the east-west direction between solar tracking unit 2202a of solar tracking assembly 2100 a and corresponding solar trackingunit 2202 b of solar tracking assembly 2100 b.

FIG. 24B shows that this example of a tracker assembly can be 1.554 m inheight h₁ from the ground to the top of the armature (not shown in FIG.24B), and 0.678 m in height h₂ from the ground to the upper chord member2014. In the examples of FIGS. 24A-24C, the tracking units each holdsolar panels 2210 comprising three solar panel modules 2205; therefore,in this particular example, twelve solar panel modules 2205 aresupported by each tracker assembly 2100. Additional specifications forthis example implementation of a tracker assembly are as follows: themaximum solar panel area per tracker assembly is 21 m²; the trackerweight is 195 kg; the maximum wind speed in stow position is 120 mph;the maximum operational wind speed is 35 mph; the tracking accuracy isless than 2 degrees; the azimuth control angle is 360 degrees; theelevation control angle is 20-95 degrees; the electrical powerrequirements are 85-265 V AC, 50 hz or 60 hz for single and split phaserespectively; the theoretical nominal power consumption is 35.0kWh/year; the operational temperature is −20 to 50° C. and the storagetemperature is −40 to 85° C. Those skilled in the art will understandthat these dimensions are not mandatory; other dimensions andconfigurations can be used depending on the specific application and maybe dependent on the solar panel dimensions or other constraints andconditions. In addition, communication to the individual solar trackingassemblies or units mounted on each leg assembly may be achieved via apower line or USB. As mentioned above, the operator may control theassemblies and units by issuing commands over a network. This caninclude wireless transmission to the global control unit as well aswireless transmission from the global control unit to the LPUs.Communication between the LPUs and individual solar tracking units maybe wireline (e.g. the power line or USB connection mentioned above)rather than wireless.

It can be appreciated from FIGS. 23 and 24C in particular that a rhombusframe such as that of FIG. 17 and the following figures, discussedabove, makes possible a particular configuration of solar trackerassemblies 2100 in the field unlike the rectangular grid arrangement ofFIG. 14 or 16. As can be seen in the example of FIGS. 23 and 24C, thefield comprises a set of solar tracker assemblies 2100 arranged suchthat adjacent sides of adjacent solar tracker assemblies 2100 areparallel. However, as most clearly seen in FIG. 24C, the result is thatthe individual solar tracking units, the positions of which aredetermined by the position of leg assemblies on which the individualsolar tracking units are mounted, are arranged in a staggered formationwith in substantially equally-spaced rows and columns.

This is further illustrated in FIG. 25A, which depicts another exampleof a field of interconnected solar tracker assemblies having anoblique-angled (i.e., non-square) rhombus or diamond frame as generallydescribed above. In this figure the spacing arms 2302, 2304 have beenomitted to reduce clutter in the drawings, but it will be understood bythose skilled in the art that the physical spacing and interconnectioncan be accomplished using the spacing arms 2302, 2304 as describedabove. In this example field, eight solar tracker assemblies 2500 a to2500 h are illustrated with in a similar arrangement to the nine solartracker assemblies 2100 of FIG. 23 or 2100 a to 2100 d of FIG. 24C; inother words, with all solar tracker assemblies oriented in the samedirection, with adjacent sides of each solar tracker assembly (asdefined by the sides of that assembly's rhombus frame) being parallel tothe immediately adjacent (i.e., nearest neighbour) solar trackerassembly. There may, of course, be more or fewer solar trackerassemblies and solar tracking units than illustrated in these examples.As illustrated, each solar tracker assembly 2500 a to 2500 h is providedwith four solar tracking units a, b, c, and d. However, it will beunderstood by those skilled in the art that each assembly need not beprovided with a full complement of solar tracking units; a single solartracking assembly may be provided with between zero and four solartracking units. The solar tracking units are generally presumed to becollocated with a corresponding leg assembly (not shown in FIG. 25A),the leg assembly thus defining the position of the solar tracking unitwith respect to the other solar tracking units in a single assembly 2500a, as well as with respect to other assemblies 2500 b to 2500 h in thefield. In the discussion of spacing, orientation and arrangement ofsolar tracker assemblies herein, references to the position of the legassembly and the position of the solar tracking unit may be usedinterchangeably.

As in the case of FIGS. 23 and 24C, the cross member of each solartracker assembly may be substantially aligned with the north-southdirection indicated as direction D₁ (the east-west direction istherefore D₂), but as will be discussed below, the physicalinterrelationship among the set of tracker assemblies does not requireorientation in a cardinal direction. FIG. 25A shows an overlay of partof a rectangular grid having rows 2502 a to 2502 d, aligned to besubstantially collinear or parallel with the major diagonals of a set ofthe solar tracker assemblies, and columns 2504 a to 2504 d, which aresubstantially collinear or parallel with the minor diagonals of a set ofthe solar tracker assemblies (i.e., substantially collinear with a setof cross members within the entire group of assemblies). Each of theserows and columns contains a set of one or more solar tracking units.Thus, for example, row 2502 b is collinear with the major diagonal (notmarked) of solar tracker assemblies 2500 a and 2500 b, and contains foursolar tracking units (units d and b of both assemblies 2500 a and 2500b). Row 2502 d is collinear with the major diagonals of solar trackerassemblies 2500 c and 2500 d and contains four solar tracking units aswell (units d and b of assemblies 2500 c and 2500 d). Rows 2502 a and2502 b are each parallel to the remaining rows, and are consequentlyparallel to the major diagonals of the solar tracker assemblies 2500 ato 2500 h. Row 2502 a contains two solar tracking units, unit a of bothassemblies 2500 a and 2500 b. Row 2502 c contains four solar trackingunits, unit c of assemblies 2500 a and 2500 b, and unit a of assemblies2500 c and 2500 d. Column 2504 a contains four solar tracking units,unit d of assemblies 2500 b and 2500 f, and unit b of assemblies 2500 cand 2500 g. Columns 2504 b, 2504 c, and 2504 d similarly contain foursolar assemblies from different sets of solar tracking assemblies. Assmall height variations may exist between adjacent frames or legassemblies due to variations in the terrain, “collinear” includes thosecases where there is no true collinearity but the sides, cross members,or spacing arms in question are substantially collinear for practicalpurposes, for instance where both members lie in planes that aresubstantially coincident.

As an aside, it will be appreciated by those skilled in the art that thegeometry of a rhombus or diamond shape generally comprises twodiagonals, extending between opposing vertices of the rhombus. Thelesser diagonal extends between the two closer vertices, while thegreater diagonal extends between remaining vertices, which are furtherapart. Of course, in a square rhombus where the angles defined at eachvertex is 90°, the diagonals will be of equal length; however, asillustrated in the accompanying figures and as discussed above, therhombus frames in these examples are non-square or oblique-angled. Asexplained above, the cross members 2046 of each frame connect the legassemblies that are closer to each other, and are thus substantiallyaligned with the lesser diagonal. The cross members and lesser diagonalsof the solar tracker assemblies 2500 a to 2500 h (or in a field of anynumber of similarly positioned assemblies) may thus be considered to bemore or less collinear or parallel. The length of the cross member maynot be the exact length of the lesser diagonal, allowing for thedimensions of the leg assemblies to which the cross member is attached,and any fastening means provided on the cross member or leg assemblies.

Returning to FIG. 25A, it can be seen that, by virtue of the physicalspacing between the frames of adjacent solar tracker assemblies 2500 ato 2500 h and the rhombus (diamond) configuration of the solar trackerassembly frames, adjacent rows and columns of solar tracking units arealternately staggered; thus, assuming that the field is aligned with thecardinal directions as indicated in FIG. 25A, nearest neighbour (bydistance between leg assemblies) of a given solar tracking unit is notdirectly to the north or south; for example, compare unit b of assembly2500 a, with nearest neighbours a and c of assembly 2500 a and unit a ofassembly 2500 c. The next solar tracking unit directly to the south(i.e., in a line substantially parallel with D₁ and with a row asdefined above) is not the nearest neighbour.

The physical spacing and frame shape is preserved even when the field asa whole is oriented in a different direction. FIG. 25B illustrates thesame field of interconnected solar tracker assemblies 2500 a to 2500 h,with solar tracking units a, b, c, and d labelled as in FIG. 25A. Allassemblies are again in the same orientation with respect to each otherand spaced as described above, although in this example the entire fieldof solar tracker assemblies has been rotated such that a side of eachframe is substantially parallel with the direction D₁ (which as notedabove may be a cardinal direction). Given the parallelogrammatic shapeof the frames, each frame of the assemblies 2500 a to 2500 h accordinglyhas a pair of sides substantially parallel with this direction. Rotationof the field in this manner gives rise to an advantageous field layout,discussed below. The rectangular modules (e.g., solar panels) carried byeach solar tracking unit have been rotated in FIG. 25B to have the samealignment with respect to D₁ as those modules in FIG. 25A. Once again,it can be seen that in a set of rows 2506 a to 2506 d and columns 2508 ato 2508 d aligned with orthogonal directions D₁ and D₂, respectively,the field of assemblies 2500 a to 2500 d yields sets of staggered rowsor columns of solar tracking units. Thus, the solar tracking units inrow 2506 a (unit a of assembly 2500 a, unit d of assembly 2500 c, andunit a of assembly 2500 g) are evenly spaced with respect to each other,and staggered with respect to the solar tracking units in row 2506 b(unit c of assembly 2500 a, unit b of assembly 2500 e, and unit c ofassembly 2500 g), which themselves are evenly spaced in their own row.Similarly, the solar tracking units in a given column such as 2508 a(consisting of six a and d units from three different tracker assemblies2500 d, 2500 f and 2500 g) are staggered in relation to the solartracking units in an adjacent column, such as 2508 b (consisting of sixb and c units from the same three tracker assemblies). It can be seenthat a given row or column need not have the same number of solartracking units as its neighbouring rows or columns, or indeed as anyother row or column.

It can further be recognized that the layout of solar tracking units ina field arranged as in FIGS. 23, 24C, 25A and 25B can be definedaccording to other schemas. For instance, the staggered spacing of thesolar tracking units may be expressed in the form of a diamond grid asillustrated in FIG. 25C, with each solar tracking unit of a given solartracking assembly occupying a distinct diamond cell within the grid.Thus, as indicated in FIG. 25C, in solar tracker assembly 2500 a, solartracking units a to d occupy corresponding diamond cells 2512 a to 2512d, and in solar tracker assembly 2500 b, solar tracking units a to doccupy corresponding diamond cells 2514 a to 2514 d. It can be seen thatthe diamond cells in this configuration tile the area covered by thefield of solar tracker assemblies 2500 a to 2500 h.

An alternate expression is shown in FIGS. 25D and 25E. These figuresillustrate that the same layout of the solar tracking units may bedefined by a hexagonal grid layout, where each solar tracking unitoccupies a corresponding hexagonal cell, the hexagonal cells tiling thearea covered by the field. Thus, the solar tracking units a to d ofsolar assembly 2500 a occupy corresponding hexagonal cells 2522 a to2522 d, and solar tracking units a to d of solar assembly 2500 b occupycorresponding hexagonal cells 2524 a to 2524 d. Each solar tracking unitin the hexagonal grid can have between two and six immediate neighbours(i.e., separated by the shortest distance). Unit b of solar trackerassembly 2500 d has only two neighbours, units a and c of the sameassembly 2500 d; unit a of assembly 2500 f has six neighbours, includingb, c, and d of its own assembly 2500 f, as well as unit b of assembly2500 c, unit c of assembly 2500 b, and unit d of assembly 2500 d.

The hexagonal grid schema gives rise to a further definition of thelayout, illustrated in FIG. 25E. It can be seen that the hexagonal gridcan be subdivided into sets of adjacent, contiguous cells or clusters,each comprising a central cell (e.g., the cell containing unit d ofassembly 2500 c) and six immediately adjacent cells (e.g., units b and cof assembly 2500 a, units a and c of assembly 2500 c, and units a and bof assembly 2500 e). Some such clusters may be complete clusters ofseven cells, as in the case of clusters 2526 a and 2526 b; otherclusters may be partial due to the layout of the solar trackerassemblies, as in the case of clusters 2526 c and 2526 d. As mentionedearlier, control of each solar tracking unit in a given assembly may beprovided by an LCU, not shown; in each cluster of the cellulararrangement, the solar tracking units may be controlled by up to fourdifferent LCUs.

As mentioned above, rotation of the field of solar tracker assembliesfrom the orientation shown in FIG. 25A can result in an advantageousfield layout. One such layout is illustrated in FIG. 26A. This figureillustrates an example field of eight solar tracker assemblies 2600 a to2600 h, each having the same orientation, in this case each frame havinga pair of sides substantially parallel to a first direction D₁. Thispair of sides includes side 2612 b on each frame. The remaining sides ofeach frame, which include sides 2612 a, are of course parallel to oneanother within each frame, and are also parallel to the correspondingsides of each other frame in the field. Again, D₁ may be a cardinaldirection, such as north or south, and the other direction D₂,perpendicular to D₁, can be east or west. The tracker assemblies arenotionally arranged into a set of parallel columns or rows: here, fourcolumns (assemblies 2600 a, 2600 e; assemblies 2600 b, 2600 f;assemblies 2600 c, 2600 g; and assemblies 2600 d, 2600 h) and two rows(assemblies 2600 a to 2600 d, and assemblies 2600 e to 2600 h). Thesecolumns are thus parallel with the sides of the frames that aresubstantially parallel with D₁.

Because the tracker assemblies 2600 a to 2600 h are arranged with a sideparallel to the first direction D₁, the entire field of tracking unitsand tracker assemblies defines a generally rectangular area, with sidesparallel to D₁ and D₂. Arranging the field in this manner provides forefficient usage of the land available for erecting a farm of solartracking assemblies, which is often divided into parcels having boundarylines and access roads running north-south.

As set out earlier, the individual frames may be interconnected withspacing arms. In the example of FIG. 26A, spacing arms 2602 connectadjacent frames within a given column and are substantially collinear(and consequently substantially parallel) with a first side of eachframe in the column. The spacing arms 2602 in other columns are likewisecollinear and parallel with the corresponding side of their respectiveframes, here marked as side 2612 b. These spacing arms define thespacing between the frames, and consequently between the solar trackingunits of adjacent frames, within a given column, in the first directionD₁.

The spacing of adjacent columns is controlled by a second set of spacingarms 2604, which here are shown as substantially collinear and parallelwith the cross members 2646 of each assembly 2600 a to 2600 h. Thesecross members 2646, as discussed above, may be aligned with the lesserdiagonal of each rhombus frame. The second set of spacing arms isaccordingly not parallel with a side of the frames.

The arrangement of FIG. 26A differs from that of FIG. 25A in that notonly are the solar tracker assemblies 2500 a to 2500 h of FIG. 25Astaggered, but the solar tracking units a, b, c, d are, likewise; but inFIG. 26A, the solar tracker assemblies 2600 a to 2600 h are notstaggered, but the solar tracking units a, b, c, d are still staggered.The arrangement of FIG. 26A thus yields the staggered layout of solartracking units, but accomplishes this with aligned columns and rows ofsolar tracking assemblies, rather than with a staggered arrangement. Thestaggered arrangement of solar tracking units is illustrated in FIG. 26Bin a manner similar to that of FIGS. 25A and 25B, with rows of solartracking units 2562 a, 2562 b, 2562 c, and 2562 d parallel to directionD₂, and columns of solar tracking units 2654 a to 2654 d parallel todirection D₁. It will be easily appreciated from the drawing that thearrangement of solar tracking units remains staggered, by comparing thearrangement of units in adjacent rows or columns to one another.

The staggered arrangement of solar tracking units can, again, be definedin terms of the hexagonal grid and the cellular clusters discussed inconnection with FIGS. 25D and 25F. As shown in FIG. 26C, a first clusterof hexagonal cells 2626 a contains solar tracking unit c of solartracker assembly 2600 a at its center, surrounded by adjacent cellscontaining units b and d of solar tracker assembly 2600 a, unit d ofassembly 2600 b, units a and b of assembly 2600 e, and unit a ofassembly 2600 f. This first cluster accordingly comprises solar trackingunits from four different solar tracker assemblies and four differentadjacent frames; consequently, this first cluster includes solartracking units controlled by four different LCUs. Solar tracking unit cof solar tracker assembly 2600 a has six neighbouring solar trackingunits; other units may have fewer neighbouring units, such as unit a ofsolar tracker assembly 2600 a, which has only two. FIG. 26C includesanother complete cellular cluster 2626 b; other clusters 2626 c, 2626 dare incomplete due to the arrangement of solar tracker assemblies.

An alternative layout of solar tracking units and solar trackerassemblies, which also provides the substantially rectangular field, isshown in FIG. 27A. Like the arrangement of FIG. 26A, all frames of thesolar tracking assemblies 2700 a to 2700 h have a pair of sides,including sides 2712 a indicated in the drawing, that is substantiallyparallel to the first direction D₁. The remaining pair of sides in eachframe remains parallel to each other, within each frame; however,alternating columns of frames comprise sets of solar tracker assembliesof opposite orientations, so these sides are not all parallel to eachother within the entire field. Sides 2712 b, indicated in FIG. 27A foreach solar tracker assembly, has different orientations according to thecolumn in which the assembly is located.

Again, the tracker assemblies are notionally arranged into sets ofparallel columns. In this example, there are four columns (solar trackerassemblies 2700 a and 2700 e; assemblies 2700 b and 2700 f; assemblies2700 c and 2700 g; and assemblies 2700 d and 2700 h). In each of thesecolumns, pairs of sides are substantially parallel with D₁. Of theremaining sides, the adjacent sides of adjacent solar tracker assemblies(e.g. 2700 a, 2700 e) are parallel. Adjacent columns of solar trackerassemblies, on the other hand, are arranged in opposing (effectivelymirror image) orientations, such that the lesser diagonals (and crossmembers 2746) are arranged in opposing directions. If D₁ is north, thenthe cross member 2746 of solar tracker assembly 2700 a is aligned alonga west-northwest to east-southeast direction, while the cross member2746 of solar tracker assembly 2700 b, in an adjacent column, isassigned in an east-northeast to west-southwest direction. The preciseheading of these directions will depend on the specific frame geometryemployed in the field. The effect is that not every cross member 2746,or every side 2712 b of all frames in the field, will be parallel.

The individual frames of each assembly may be interconnected withspacing arms. As with the example of FIG. 26A, spacing arms 2702 a, 2702b connect adjacent frames within a given column, and are substantiallycollinear or parallel with a corresponding side of each frame in thecolumn. Thus, in the first and third columns of assemblies (assemblies2700 a, 2700 e; and 2700 c, 2700 g), the spacing arms 2702 a aresubstantially collinear with sides 2712 a, and are consequently parallelwith direction D₁. However, in the example of FIG. 27A, for theremaining columns of assemblies (2700 b, 2700 f; 2700 d, 2700 h) spacingarms 2702 b, which are parallel with direction D₁ as well, are notcollinear with the corresponding sides 2712 a of the frames to whichthey are attached, but are rather collinear with the opposite side to2712 a. Spacing arms 2702 b could alternatively be attached to theframes of those columns so as to be collinear with sides 2712 a.

The spacing of adjacent columns is controlled by a second set of spacingarms 2704 a and 2704 b. Because of the opposing orientations of adjacentcolumns, the position of these spacing arms will vary by column. Spacingarms 2704 a are collinear with sides 2712 b of the solar trackerassemblies of the first and third columns; spacing arms 2704 b arecollinear with the cross members 2746 of the solar tracker assemblies ofthe second and fourth columns. In this example, the result is that allspacing arms 2704 a, 2704 b are parallel to each other. In an alternateembodiment, spacing arms 2704 b may be aligned in an opposing direction(e.g., between unit b of assembly 2700 b, and unit d of assembly 2700c).

As with the example of FIG. 26A, the solar tracking units a, b, c, d ofall of the solar tracker assemblies in the field are staggered, whilestill providing aligned columns of solar tracker assemblies andgenerally aligned rows of solar tracker assemblies, that fit within agenerally rectangular area. The staggered arrangement of solar trackingunits can, as before, be defined in terms of a hexagonal grid andcellular clusters. FIG. 27B illustrates a parceling of hexagonal cellsinto clusters 2726 a to 2726 d. Complete clusters 2726 a and 2726 b thusinclude seven contiguous cells, and their central solar tracking units(unit c of solar tracker assembly 2700 a, and unit d of solar trackerassembly 2700 c) have six neighbours, while others, such as unit d ofassembly 2700 f has only four. Clusters 2726 a and 2726 b contain solartracking units associated with three different solar tracker assemblies,and thus three different LCUs. This is not the only subdivision of thehexagonal grid possible. FIG. 27C illustrates an alternate set ofclusters 2728 a to 2728 d, where cluster 2728 a includes solar trackingunits from four different solar tracker assemblies.

As those skilled in the art will appreciate, shading from adjacent solarpanels is a concern when multiple solar tracking units are erected inproximity to one another. Particularly at the beginning and end ofdaylight, the angle of incident sunlight on a PV panel may cause the PVpanel to cast a shadow on one or more adjacent panels, thus reducing theadjacent panels' performance. In some solutions, a backtrackingalgorithm is employed to compute optimum angles—which may bedifferent—for each PV panel within a field in order to minimize shading.Backtracking, and other optimization solutions, are used to remedy thedefects that arise in solar farms after deployment, whether thesedefects arise due to issues such as shading, environmental conditions,installation errors, or manufacturing defects within the PV modulesthemselves. The shading issue, in particular, is one that arises due tothe physical arrangement and spacing of solar tracking units in thefield. On the one hand, one might consider that an increase in thenumber of solar tracking units in the field will improve the yield ofthe entire field; on the other hand, when available space for erectingthe field of solar tracking units is constrained, extra solar trackingunits may only be accommodated by moving the existing units closertogether, which increases the potential for a loss of efficiency andoverall performance due to shading.

The hexagonal grid arrangement of solar tracking units illustrated inthe foregoing drawings has been found to provide improved performanceover the rectangular or square grid arrangement otherwise possible usingthe same sets of frame sides or trusses, by reducing the incidence ofshading between adjacent solar panels. Table 1, below, sets out modelleddata on a month-by-month basis for a hexagonal grid and rectangular gridsystem comprising an identical number of solar tracking units, eachequipped with a 2.99×1.67 meter PV panel with 15.48% efficiency at alatitude of 34.73° N. The rectangular model was based on an arrangementof sixteen solar tracker assemblies with four solar tracking unitsapiece in a 4×4 rectangular grid, with solar tracking units separated by4.1 meters in the east-west direction, and 4.7 m in the north-southdirection. The hexagonal model was based on an arrangement of thesixteen solar tracking assemblies arranged as in FIG. 26A, again withseparation of units by 4.1 meters in the east-west direction and 4.7 min the north-south direction. Table 1 provides the calculated yield inkWh for the hexagonal and rectangular grid models, based on the averageoutput of the solar panel mounted at or near the center of the entiregrid, and taking into account shading effects due to other panels in thegrid. As can be seen in Table 1, the hexagonal grid arrangement yieldedimproved performance during most months of the year, and overall about a3% improvement over the rectangular grid arrangement.

TABLE 1 Month Hexagonal Rectangular % Difference January 107.9 102.45.37 February 121.6 113.2 7.42 March 162.7 154.2 5.51 April 181.9 178.41.96 May 203.1 203.8 −0.34 June 202.7 205.7 −1.46 July 207 208.3 −0.62August 194.5 192.8 0.88 September 167.4 161.1 3.91 October 145.9 135.97.36 November 111.6 105.4 5.88 December 101.1 96.3 4.98

Table 2, below, compares the performance of the hexagonal andrectangular grid arrangements by latitude over a year. The hexagonalarrangement resulted in an increase in power output of about 2-4% peryear over the rectangular arrangement, depending on the latitude of thefield.

TABLE 2 Latitude Hexagonal Rectangular % Difference 0 2145.8 2091.4 2.6010 2128.7 2059.7 3.35 20 2075.8 2014 3.07 30 1976.6 1917.4 3.09 34.71907.7 1857.1 2.72 40 1816 1776 2.25 50 1589.7 1558.5 2.00 60 1332.51303.4 2.23 70 1135.2 1094.2 3.75

The arrangement of solar tracking units in a hexagonal arrangement asdescribed above thus provides some relief from the effect of interferingshading from nearby units. In cases where a prefabricated system such asthe frame assembly described herein is employed and/or where availableland for erecting a solar farm is available, the ability to arrange theassemblies as described herein provides an advantage over the prior art.As can be seen from the examples described above, a rhombus frameconfiguration can be obtained from the same trusses or sides used toconstruct a square frame, and the predetermined lengths of the framesides, cross members, and spacing arms provides for efficient andrelatively quick assembly in the field. In a further variation,discussed in greater detail below, the cross member of the solar trackerassembly can be adjustable in length, providing for flexibility inlayout when the solar tracker assembly is deployed in the field.

In addition to physical interconnection of frames 2010 of the solartracker assemblies 2100 for the purpose of enhancing stability, theindividual solar tracking units 2200 are interconnected within a singlesolar tracker assembly 2100. This is illustrated in relation to therhombus frame of FIG. 18. A local control unit 2402 (LCU) can beprovided on each assembly 2100 to control all solar units 2200 providedon a single frame 2010. Alternatively, a single LCU 2402 can be used tocontrol the solar tracking units 2200 on several frames (not shown). Forexample, a cluster of frames 2010 could be positioned and arranged suchthat an LCU 2402 is mounted only to a single frame 2010 of the clusterand the other frames 2010 do not have local control units mountedthereto. Wires can be run from the single LCU 2402 to each of the solartracking units 2200 on the frames of the cluster. Within a given frame2010 having four solar tracking units 2200, pairs of the units 2200 maybe connected in series with one another, and these pairs connected inparallel with one another, thus permitting increased voltage to reducepower losses in interconnecting wires. Each pair of units 2200 can beprovided with a current and/or voltage sensor (not shown) incommunication with the LCU 2402. In some examples, individual solartracking units 2200 on a single frame are independently controllable andeach solar tracking unit 2200 can be provided with a current and/orvoltage sensor. The LCU 2402 can use a die cast aluminium enclosure thatserves as a heat sink. The electrical system and communication oftracker assembly 2100 is generally similar to the diagram of FIG. 15,and any elements not described in relation to this embodiment can befound in the description of the embodiments above.

In the example illustrated in FIGS. 17 and 18, armatures 2080 and thesolar tracking units 2200 are mounted on a mounting end 2035 of the legassemblies 2030. The solar tracking unit 2200 includes an armatureassembly 2080, shown in FIG. 28. A solar panel may be mounted on each ofthe armature assemblies 2080. Each solar tracking unit 2200 can also beprovided with a sun position sensor (not shown) for use in computerizedcalibration to ensure that sunlight is normally incident on the surfaceof the solar panel, and to compensate for the vagaries of the fieldinstallation such as uneven terrain affecting the pitch of a given unit2200, and other issues such as manufacturing errors in the manufactureof the solar panel 2210 or its components, differences between theactual sun position and expected sun position, and the like.

The armature assembly 2080 includes a shaft 2082 including a lip 2098provided with boreholes that match the fasteners (for example pressfitted studs) 2045 described in FIG. 19A. The orientation of the shaft2082 with regards to the leg assembly 2030 can be determined by thefasteners 2054 and boreholes, as these can only be matched in apredetermined orientation, such that the solar tracking units 2200 arealways properly aligned. During assembly, cables 2099 running throughthe shaft 2080 are connected to cables in the leg assembly 2030, beforefixing the armature 2080 on the leg assembly. Once the cables have beenproperly connected, the boreholes of the lip 2098 can be matched tofasteners 2045 of the upper lip 2043 and then they can be secured bymeans of a bolt or any other fastening means.

The armature assembly includes a yoke 2084 provided with a yoke mount2079, a crosspiece 2085 extending from the yoke mount 2079, and firstand second arms 2086 extending from the crosspiece 2085. In theconfiguration shown in FIG. 28, the arms 2086 extend substantiallyperpendicularly from the crosspiece 2085 and are substantially parallelto the yoke mount 2079 and to each other, although in otherconfigurations their relative position with respect to the crosspiece2085 and the yoke mount 2079 may vary according to the design of thesolar panel mounted on the armature assembly 2080. In this embodiment nogusset is required. The yoke mount 2079 extends through and is fixed tothe center of crosspiece 2085. The yoke mount 2079, the crosspiece 2085and the arms 2086 may be manufactured as individual components weldedtogether to form the yoke 2084. Alternatively, the yoke 2084 may beintegrally formed as a single part by die casting.

A bearing or bushing, may be provided within the yoke mount 2079 tofacilitate rotation of the yoke 2084 about shaft 2082. A first drivesystem for controlling yaw movement of the solar tracking unit 2200includes a first gear wheel 2090 fixed to the shaft 2082, and thereforestationary relative to the frame 2010. A second gear wheel 2091 inengagement with the first gear wheel 2090 is also provided on thecrosspiece 2085, extending from the same face of the crosspiece 2085 asthe first gear wheel 2090. The second gear wheel 2091 is fixed relativeto the yoke 2084. In the example of FIG. 28, the first and second gearwheels 2090, 2091 are disposed on the inside of the yoke 2084, i.e.,between the arms 2086. A first drive assembly including a motor andgearbox 2092 is provided for the second gear wheel 2091 for controllingrotation of the second gear wheel 2091 to cause the yoke 2084 to rotatearound the fixed first gear wheel 2090 and the shaft 2082. An example ofa suitable drive assembly includes a weatherproof and durable steppermotor having an output shaft connected to a sealed gearbox that has anoutput shaft with a pinion gear (the second gear wheel 2091). The piniongear (the second gear wheel 2091) can therefore provide higher torquethan the stepper motor, the increase in torque depending on the gearratios of the gears contained inside the sealed gearbox. The pinion gearconnected to the output shaft of the sealed gearbox engages the firstgear wheel 2090 and can operate in an unsealed environment. The firstdrive system thus provides for rotation of the yoke 2084 up to 360degrees (or greater) in a clockwise or counter-clockwise direction. Inuse, the armature assembly 2080 may be enclosed in a weatherproof cover(not shown) to protect the drive systems from ice, rain, sand, etc.

An axle 2088 is mounted on concave portions 2087 provided near the endsof the two arms 2086. Again, appropriate bearings or bushings 2081 maybe provided, for example bushings manufactured by Igus GmbH. Each end ofthe axle 2088 terminates in a plate 2089 for mounting to an underside ofa solar panel. The precise configuration of the plates 2089 will dependon the attachment means used to mount the solar panel to the armatureassembly 2080; in this case, grooves are provided in the perimeter ofthe plate 2089 to receive fasteners to join the armature assembly 2080to the solar panel. A second drive system controlling pitch of the solartracking unit 2200 is provided on the yoke 2084 and axle 2088; a firstgear wheel 2095 is mounted on the axle 2088, and a second gear wheel2096 in engagement with the first gear wheel 2095 is mounted on the yoke2084. In this example, the first gear wheel 2095 is a circular sectorwheel rather than a full circle like the gear wheel 2090. Since yaw overa wider range (i.e., over 180 degrees) may be provided by the firstdrive assembly comprising the gear wheels 2090, 2091, pitch adjustmentof the solar tracking unit 2200 over a range of 95-150 degrees is likelysufficient. In other examples, the gear wheel 2095 may be a semicircularshape rather than a quarter-wheel; depending on the proximity of thesolar panel to the axle 2088, it may not be possible to provide afull-circular gear wheel on the axle 2088. The second gear wheel 2096 iscontrolled by a further drive system including a motor and gearbox 2097,also mounted on the yoke 2084. An example of a suitable drive assemblyincludes a weatherproof and durable stepper motor having an output shaftconnected to a sealed gearbox that has an output shaft with a piniongear (the second gear wheel 2096). The pinion gear (the second gearwheel 2096) can therefore provide higher torque than the stepper motor,the increase in torque depending on the gear ratios of the gearscontained inside the sealed gearbox. The pinion gear connected to theoutput shaft of the sealed gearbox engages the first gear wheel 2095 andcan operate in an unsealed environment. In the example of FIG. 28, themotor 2097 and second gear wheel 2096 are mounted on the arm 2086proximate to the gear wheel 2095.

In FIG. 28, spur gears are illustrated; however, other types of gearsmay be employed as well to provide motion in the two substantiallyorthogonal planes perpendicular to the shaft 2082 and axle 2088. Tensionsprings, not shown, may be provided to ensure engagement between theteeth of the gears 2091, 2096 and 2090, 2095. Home switches, not shown,may be provided on each of the two drive assemblies for use in returningthe solar panels to a default position. Both the motors 2092 and 2097are controllable using a local control unit described below.

The solar panel mounted to the armature assembly 2080 may take anysuitable shape. For example, the solar panel can include one or moreflat plate solar panel modules made of semiconductors such as silicon,gallium arsenide, cadmium telluride, or copper indium gallium arsenideor can be a concentrated solar panel employing concentrating optics, orheliostat mirrors. In the case of concentrated solar panels, the solarpanels include individual optical modules comprising PV cells. Theoptical modules may or may not include integrated electronics such aspower efficiency optimizers and the like. Optics provided with theindividual optical modules may include multiple-component optics. Theindividual optical modules may be combined in series in strings ofoptical modules, which in turn may be connected in parallel with otherstrings to yield an array of optical modules. One or more strings ofoptical modules can be arranged in a plane to form a solar panel module.

As mentioned above, the cross members 2046 of the solar trackingassemblies may be adjustable in length. This permits the frames of thesolar tracker assemblies to be deployed with different spacing betweenthe leg assemblies. An example implementation of an adjustable-lengthcross member 2946 is illustrated in FIGS. 29A to 29C. FIG. 29A shows thecross member 2946 mounted in a frame assembly similar to that shown inFIGS. 18, 18 and 21. In this example, the cross member 2946 is a simplechord assembly formed of suitable material, such as extruded or drawnmetal. The length adjustability of the cross member 2946 in this exampleis provided by a telescoping configuration from two nesting chordmembers 2950, 2960. As can be seen in FIGS. 29A and 29B, the first chordmember 2950 in this example is conveniently shaped as a channel beam orC-bar having two sidewalls 2952 depending from a plate 2953, thusdefining a channel with an open end 2954 for receiving the second chordmember 2960. The channel is sized to receive the second chord member2960, which in this example is a rectangular beam. The combined lengthof the first and second chord members 2950, 2960 is greater than thegreatest required length for the cross member 2946.

The first chord member 2950 is provided with boreholes 2955 nearer thereceiving (open) end 2954. These bore holes can be spaced by incrementswhich can be used to define different finished lengths for the crossmember 2954, e.g., every 10 or 15 cm. The second chord member 2960 isprovided with corresponding boreholes 2965 nearer an engagement end2964, which engages the receiving end 2954 of the first chord member2950. The engagement end 2964 of the second chord member 2960 isaccordingly inserted into the receiving end 2954 of the first chordmember 2950 until the total length of the two members 2950, 2960 is at adesirable length, and at least one set of corresponding boreholes 2955,2965 is aligned. Suitable fasteners, such as screws, are engaged in thecorresponding boreholes to fix the members 2950, 2960 together. Theboreholes 2965 are advantageously spaced by the same increments as theboreholes 2955 so that when the two members 2950, 2960 are engaged, aplurality of boreholes of both members 2950, 2960 are aligned and canreceive fasteners. Other profiles and fastening means for the first andsecond chord members 2950, 2960 may of course be employed; for instance,the chord members may be telescoping tubular members (channel or closed)that can also comprise the boreholes described above, or may compriseflat plates or other members with substantially flat contact surfaceswhere fasteners are applied.

The cross member 2946 can be fixed to opposing leg assemblies 2030 muchin the same manner described with reference to FIGS. 19A to 19C.However, since the overall length of the cross member may vary, theangles of the rhombus frame 2010 will likewise vary. The brackets orother means used to attach the trusses 2012 forming the sides of theframe 2010 are therefore adapted to accommodate changes in theattachment angle. FIG. 29C illustrates brackets 2970 which are similarto those brackets 2049 described above with reference to FIG. 19A, butare wider to accommodate different positions of the truss 2012. As canbe seen in FIG. 29C, an upper bracket 2970 a is provided with at leastone curved slot 2972, sized to receive the bolt or other fastener usedto attach the truss 2012 to the leg assembly 2030. The truss 2012 cantherefore be inserted between the upper bracket 2970 a and a lowerbracket 2970 b at the desired angle, and positioned so that a boreholeon the truss 2012 registers with the slot 2972. The fastener 2974 canthen be inserted in the aligned slot and borehole. Alternatively, anumber of boreholes, rather than a single slot, may be provided in theupper bracket 2970 a, or else a number of straight slots extendingradially along the bracket, to allow for flexibility in positioning thetruss 2012 at the leg assembly 2010.

Various embodiments of the present invention having been thus describedin detail by way of example, it will be apparent to those skilled in theart that variations and modifications may be made without departing fromthe invention. The invention includes all such variations andmodifications as fall within the scope of the appended claims.

1. A field of interconnected solar tracking units, the field comprising:a plurality of solar tracking units arranged in a hexagonal gridarrangement, each solar tracking unit of the plurality of solar trackingunits having between two and six neighboring solar tracking units,wherein movement of each solar tracking unit of the plurality of solartracking units in relation to at least one axis of said solar trackingunit is controlled by a local control unit, each local control unitcontrolling up to four solar tracking units of the plurality of solartracking units, said up to four solar tracking units being mounted on asingle oblique-angled, rhombus frame associated with said local controlunit.
 2. The field of interconnected solar tracking units of claim 2,the field thus comprising a plurality of frames, each frame comprisingfour leg assemblies connected by sides of substantially equal length,the leg assemblies being adapted for mounting a corresponding solartracking unit, the frame comprising a greater diagonal defined by adistance between two of the four leg assemblies separated by a greaterdistance and a lesser diagonal defined by a distance between a remainingtwo of the four leg assemblies separated by a lesser distance.
 3. Thefield of interconnected solar tracking units of claim 3, each frame ofthe plurality of frames being interconnected by at least one spacing armof predetermined length to an adjacent frame, the at least one spacingarm thus maintaining a regular spacing among the plurality of solartracking units to provide the hexagonal grid arrangement.
 4. The fieldof interconnected solar tracking units of claim 3, wherein adjacentsides of adjacent pairs of frames are substantially parallel.
 5. Thefield of interconnected solar tracking units of claim 4, each framecomprising a pair of sides substantially parallel to a cardinaldirection.
 6. The field of interconnected solar tracking units of claim5, wherein at least some of the spacing arms are substantially parallelto the cardinal direction.
 7. The field of interconnected solar trackingunits of claim 6, wherein others of the spacing arms are substantiallyparallel to either the lesser diagonal of a frame to which the spacingarm is attached, or to a side of the frame to which the spacing arm isattached other than a side of the pair of sides substantially parallelto the cardinal direction.
 8. The field of interconnected solar trackingunits of claim 7, wherein each of the frames is in substantially a sameorientation.
 9. The field of interconnected solar tracking units ofclaim 7, wherein the plurality of frames is arranged in alternatingparallel columns of frames in opposing orientations, the frames withineach column being arranged in substantially a same orientation andhaving a pair of sides substantially parallel to the column.
 10. Thefield of interconnected solar tracking units of claim 7, wherein theothers of the spacing arms interconnected adjacent columns of frames,and comprise both spacing arms parallel to the lesser diagonal of theframe to which the spacing arm is attached, and spacing arms parallel tothe side of the frame to which the spacing arm is attached other than aside of the pair of sides substantially parallel to the cardinaldirection.
 11. The field of interconnected solar tracking units of claim1, wherein the one or more solar tracking units comprise either one ormore heliostat mirrors or one or more photovoltaic modules.
 12. Thefield of interconnected solar tracking units of claim 1, wherein thelocal control unit is configured to control movement of the up to foursolar tracking units in relation to two axes.
 13. The field ofinterconnected solar tracking units of claim 1, wherein each frame isassociated with a distinct local control unit, the field ofinterconnected solar tracking units further comprising a global controlunit in communication with each distinct local control unit, the globalcontrol unit being adapted to issue instructions controlling each localcontrol unit.
 14. The field of interconnected solar tracking units ofclaim 3, each frame further comprising a cross member of a definedlength extending substantially along the lesser diagonal and being fixedto each of the two leg assemblies separated by the lesser distance. 15.The field of interconnected solar tracking units of claim 14, whereinthe plurality of solar tracking units mounted on the plurality of framesthus interconnected are mutually ballasted.
 16. A field ofinterconnected solar tracking assemblies, the field comprising: aplurality of solar tracker assemblies with a plurality of solar trackingunits mounted thereon, each solar tracker assembly comprising: anoblique-angled, rhombus frame comprising four leg assembliesinterconnected by sides of substantially equal length; and one or moresolar tracking units of the plurality of solar tracking units mounted onone or more of the four leg assemblies, movement of the one or moresolar tracking units in relation to at least one axis being controlledby a local control unit associated with the solar tracker assembly, theplurality of solar tracker assemblies being arranged such that theplurality of solar tracking units mounted thereon define a substantiallyhexagonal cellular arrangement comprising a plurality of at least twoadjacent clusters of cells of the cellular arrangement, each clustercomprising a central cell surrounded by six immediately adjacent cells,each of said clusters comprising solar tracking units controlled by atleast three different local control units.
 17. The field ofinterconnected solar tracking assemblies of claim 16, wherein at leastone of said clusters comprises six solar tracking units controlled byfour different local control units.
 18. The field of interconnectedsolar tracking assemblies of claim 17, wherein frames of adjacent solartracker assemblies of the plurality of solar tracker assemblies areinterconnected by spacing arms of predetermined length, the spacing armsthus maintaining spacing for the substantially hexagonal cellulararrangement; all of the frames having substantially the same orientationand having a greater diagonal and a lesser diagonal, all of the framesbeing arranged in columns along a first direction, at least some of thespacing arms being substantially collinear with the lesser diagonal of aframe to which the spacing arm is connected, and others of the spacingarms being substantially collinear with a side of each frame to whichthe spacing arm is connected, said side extending substantially parallelto the first direction.
 19. The field of interconnected solar trackingassemblies of claim 17, wherein frames of adjacent solar trackerassemblies of the plurality of solar tracker assemblies areinterconnected by spacing arms of predetermined length, the spacing armsthus maintaining spacing for the substantially hexagonal cellulararrangement, all of the frames having a greater diagonal and a lesserdiagonal; the plurality of solar tracker assemblies being arranged incolumns along a first direction, a first set of columns comprising a setof solar tracker assemblies arranged in a first orientation, the firstset of columns being interleaved with a second set of columns comprisinga set of solar tracker assemblies arranged in a second orientationdifferent from the first orientation, at least some of the spacing armsbeing substantially collinear with a side of a frame to which thespacing arm is connected, at least some of said sides extendingsubstantially parallel to the first direction, and others of the spacingarms being substantially collinear with the lesser diagonal of a frameto which the spacing arm is connected.
 20. The field of claim 18,wherein the first direction is a north-south direction.